Bottom Line:
The topical injection of histamine or the H(2) agonist dimaprit rescued the defective angiogenesis and granulation tissue formation in HDC(-/-) mice.In addition, macrophages in the granulation tissue were found to express HDC.Our findings indicate that histamine derived from non-mast cells plays a significant role in the angiogenesis of the inflammatory granulation tissue.

ABSTRACTWe have analyzed the role of histamine in the angiogenesis of the granulation tissue in histidine decarboxylase-deficient (HDC(-/-)) mice, mast cell-deficient mice (WBB6F1-W/W(V)), and their corresponding wild-type mice (HDC(+/+) and WBB6F(1)(+/+)). In HDC(+/+) mice, subcutaneous implantation of a cotton thread in the dorsum induced granulation tissue formation with angiogenesis, while the topical injection of anti-vascular endothelial growth factor (VEGF) IgG strongly suppressed them. In HDC(-/-) mice which showed lower VEGF levels in the granulation tissue, there was notably less angiogenesis and granulation tissue formation than in HDC(+/+) mice. The topical injection of histamine or the H(2) agonist dimaprit rescued the defective angiogenesis and granulation tissue formation in HDC(-/-) mice. There was no significant difference in the granulation tissue formation and angiogenesis between WBB6F1-W/W(V) and WBB6F1(+/+) mice. In addition, macrophages in the granulation tissue were found to express HDC. Our findings indicate that histamine derived from non-mast cells plays a significant role in the angiogenesis of the inflammatory granulation tissue.

fig6: Comparison of granulation tissue formation between WBB6F1+/+ and WBB6F1-W/WV mice. A cotton thread (1 cm, 7 mg) was implanted subcutaneously in the dorsum of each mouse. The mice were killed 5 d after the cotton thread implantation. (A) The vascular network formation around the cotton thread (a) and the subcutaneous tissue beneath the cotton thread (b). (B) The granulation tissue weight and hemoglobin levels in the granulation tissue. (C) VEGF protein levels in the granulation tissue. VEGF protein levels in the granulation tissue were determined by immunoblotting and analyzed densitometrically. Representative immunoblots from two mice in each group are shown at the top of C. The mean VEGF protein level in the granulation tissue of WBB6F1+/+ mice is set to 1.0. Values are the means from five mice with SEM shown by vertical bars.

Mentions:
To clarify whether the histamine responsible for angiogenesis was derived from mast cells, we compared the cotton thread-induced granulation tissue formation and angiogenesis in mast cell–deficient mice (WBB6F1-W/WV) with those in wild-type mice (WBB6F1+/+). We found that there was no significant difference in the granulation tissue formation, angiogenesis and VEGF levels in the granulation tissue between the two groups (Fig. 6) . In HDC+/+ mice, the implantation of a cotton thread increased the HDC activity in the tissue surrounding the implanted cotton thread including the skin, cutaneous muscle layer, subcutaneous tissues and the granulation tissue, from 1 to 5 d after implantation (Fig. 7 A). In WBB6F1-W/WV mice, although the HDC activity in the tissue was very low due to the mast cell deficiency, the cotton thread implantation induced a marked increase in HDC activity in the tissue to a similar extent as that in WBB6F1-+/+ mice (Fig. 7 B). In addition, histochemical analysis of the granulation tissue dissected 5 d after the cotton thread implantation indicated the absence of mast cells in the tissue (data not shown). However, the HDC-producing cells were shown to be infiltrating macrophages (Fig. 7 C). These findings indicate that HDC expression is induced in the nonmast cell, macrophages.

fig6: Comparison of granulation tissue formation between WBB6F1+/+ and WBB6F1-W/WV mice. A cotton thread (1 cm, 7 mg) was implanted subcutaneously in the dorsum of each mouse. The mice were killed 5 d after the cotton thread implantation. (A) The vascular network formation around the cotton thread (a) and the subcutaneous tissue beneath the cotton thread (b). (B) The granulation tissue weight and hemoglobin levels in the granulation tissue. (C) VEGF protein levels in the granulation tissue. VEGF protein levels in the granulation tissue were determined by immunoblotting and analyzed densitometrically. Representative immunoblots from two mice in each group are shown at the top of C. The mean VEGF protein level in the granulation tissue of WBB6F1+/+ mice is set to 1.0. Values are the means from five mice with SEM shown by vertical bars.

Mentions:
To clarify whether the histamine responsible for angiogenesis was derived from mast cells, we compared the cotton thread-induced granulation tissue formation and angiogenesis in mast cell–deficient mice (WBB6F1-W/WV) with those in wild-type mice (WBB6F1+/+). We found that there was no significant difference in the granulation tissue formation, angiogenesis and VEGF levels in the granulation tissue between the two groups (Fig. 6) . In HDC+/+ mice, the implantation of a cotton thread increased the HDC activity in the tissue surrounding the implanted cotton thread including the skin, cutaneous muscle layer, subcutaneous tissues and the granulation tissue, from 1 to 5 d after implantation (Fig. 7 A). In WBB6F1-W/WV mice, although the HDC activity in the tissue was very low due to the mast cell deficiency, the cotton thread implantation induced a marked increase in HDC activity in the tissue to a similar extent as that in WBB6F1-+/+ mice (Fig. 7 B). In addition, histochemical analysis of the granulation tissue dissected 5 d after the cotton thread implantation indicated the absence of mast cells in the tissue (data not shown). However, the HDC-producing cells were shown to be infiltrating macrophages (Fig. 7 C). These findings indicate that HDC expression is induced in the nonmast cell, macrophages.

Bottom Line:
The topical injection of histamine or the H(2) agonist dimaprit rescued the defective angiogenesis and granulation tissue formation in HDC(-/-) mice.In addition, macrophages in the granulation tissue were found to express HDC.Our findings indicate that histamine derived from non-mast cells plays a significant role in the angiogenesis of the inflammatory granulation tissue.

ABSTRACTWe have analyzed the role of histamine in the angiogenesis of the granulation tissue in histidine decarboxylase-deficient (HDC(-/-)) mice, mast cell-deficient mice (WBB6F1-W/W(V)), and their corresponding wild-type mice (HDC(+/+) and WBB6F(1)(+/+)). In HDC(+/+) mice, subcutaneous implantation of a cotton thread in the dorsum induced granulation tissue formation with angiogenesis, while the topical injection of anti-vascular endothelial growth factor (VEGF) IgG strongly suppressed them. In HDC(-/-) mice which showed lower VEGF levels in the granulation tissue, there was notably less angiogenesis and granulation tissue formation than in HDC(+/+) mice. The topical injection of histamine or the H(2) agonist dimaprit rescued the defective angiogenesis and granulation tissue formation in HDC(-/-) mice. There was no significant difference in the granulation tissue formation and angiogenesis between WBB6F1-W/W(V) and WBB6F1(+/+) mice. In addition, macrophages in the granulation tissue were found to express HDC. Our findings indicate that histamine derived from non-mast cells plays a significant role in the angiogenesis of the inflammatory granulation tissue.